In today's modern society, artificial outdoor lighting is increasingly used in poor natural lighting conditions, such as during night time, for various purposes, such as for increasing public safety, improving safety in traffic situations or enabling outdoor work to take place at night time.
Although providing benefits for humans, the abundant artificial outdoor lighting may have detrimental effects on animals, especially wild animals.
In particular crepuscular and/or nocturnal animals have been shown to react negatively on artificial lighting. An overview of the various effects is given in the book: ‘The ecological consequences of artificial night lighting’, edited by Rich and Longcore (Island Press, 2006, page 1-13).
One particular example of species which are affected by artificial lighting are various species of bats. Most bat species are considered to be endangered, featuring on both national and international red lists. Therefore bats are protected by a range of treaties and laws, from a global to a national level, e.g. by the international Bats Agreement, also known as the ‘Bonn Convention’.
Bats are known to avoid intense lighting. When the light levels outside their roosts is too high, they won't emerge, they will avoid ‘well’ lit areas and will not pass rows of outdoor lighting lamps forming a continuous band of light in the landscape, which in this way can block routes from living to hunting areas, severely limiting the available habitat for the bats.
Other species are also expected to be affected by excessive artificial outdoor lighting at night time.
However, drastically reducing outdoor artificial lighting during night time is not expected to be feasible, due to the positive aspects of the artificial lighting mentioned initially.